Solar light includes wavelengths in UV range that may cause human health issue. UV light with different ultraviolet index (UVI) affects human body differently. UV radiation with low UVI value causes much less damage to human body and people may be exposed by such UV radiation for a long time. But, UV radiation with high UVI value can cause high damage to human body and people needs to take certain UV protection procedures in order to be hurt due to long-time exposure. On the other hand, reasonable exposure of UV radiation with proper UVI value does provide benefit for human body to absorb Vitamin D, Calcium, Phosphorus or other elements that are good for human health.